You can get it from here
Save it to your desktop and extract the Zip file. You will be left with a .Bin file that you DO NOT RENAME.
Under Settings (All the way to the right). Select “Firmware Update” at the bottom left. Then under “Manual Update” select “Update From File”. Browse to the file then click update. Allow it to update for at least 10-20 minutes.
“”"“WARNING”"""" I recently downgraded to this Firmware as well, but in doing so I was not able to login to my Main menu interface (UI). To Fix this I removed both of my hard drives (To ensure files were not harmed) and did a reset on my WD EX2. I heald in the reset for around 40 seconds or so.